An ultra-long gravity heat pipe that overcomes hydraulic effect and enhances heat transfer

Abstract

The present invention relates to an ultra-long gravity heat pipe for overcoming the hydraulic effect and enhancing heat transfer, the heat pipe comprises an evaporation section, and is characterized in that the evaporation section is designed as a multi-layer structure, each layer comprises an outer tube, an inner tube, a groove and a fin, the groove is arranged on the inner wall surface of the outer tube, and is used for communication between layers, one end of the fin is arranged on the outer wall surface of the inner tube, wherein the other end of at least a part of the fin is connected to the outer wall surface of the groove, the inner tube is a vertical through structure, there is a certain spacing between the inner tubes of adjacent layers, and there is a connection structure between adjacent outer tubes. The evaporation section of the present invention adopts a layered structure design, the evaporation section liquid pool is divided into multiple sections, and the connection between layers is achieved through the groove structure. When the upper layer liquid level reaches the expected range, it will flow along the groove to the next layer, avoiding the problem that the working medium cannot boil due to excessive hydraulic pressure, and improving the heat transfer performance.

Description

Technical Field

[0001] The invention relates to a heat pipe technology, in particular to a super-long gravity heat pipe design for overcoming hydraulic effect and enhancing heat transfer, belonging to the heat pipe field of F28d15 / 02. Background Art

[0002] Heat pipe technology is a heat transfer element called "heat pipe" invented by George Grover of Los Alamos National Laboratory in the United States in 1963. It makes full use of the principle of heat conduction and the rapid heat transfer properties of phase change media. It transfers the heat of the heating object to the outside of the heat source quickly through the heat pipe. Its thermal conductivity exceeds that of any known metal.

[0003] Heat pipe technology was previously widely used in aerospace, military and other industries. Since it was introduced into the radiator manufacturing industry, people have changed the design ideas of traditional radiators, getting rid of the single cooling mode that simply relies on high air volume motors to obtain better cooling effects. The use of heat pipe technology enables radiators to obtain satisfactory heat exchange effects, opening up a new world for the cooling industry. At present, heat pipes are widely used in various heat exchange equipment, including the nuclear power field, such as the utilization of waste heat from nuclear power.

[0004] Geothermal energy is mainly divided into shallow geothermal energy, medium-deep geothermal energy and deep geothermal energy. Shallow geothermal energy has a temperature below 25°C and a burial depth of less than 200m; medium-deep geothermal energy has a temperature between 25–150°C and a burial depth of 200–3000m; deep geothermal energy has a temperature above 150°C and a burial depth of more than 3000m. The development of shallow geothermal energy in China has been relatively complete, but the redevelopable reserves are relatively small; deep geothermal energy is difficult to develop and has high costs due to its high temperature and deep burial depth; medium-deep geothermal energy is the focus of future geothermal energy development because it is less difficult to develop and has abundant reserves, which are about 140 times that of shallow geothermal energy.

[0005] There are three main ways to develop medium-deep geothermal energy, namely enhanced geothermal systems, downhole heat exchanger systems, and ultra-long gravity heat pipe systems. The enhanced geothermal system extracts geothermal energy through artificial storage through double or multiple wells, but there are many disadvantages such as easy loss of working fluid, easy corrosion of equipment, and easy to cause earthquakes; the downhole heat exchanger system can effectively avoid equipment corrosion and working fluid loss through single or double well closed circulation, but it requires pump power to drive the working fluid circulation, and the heat exchange efficiency is low; the ultra-long gravity heat pipe is a single well closed circulation, which can avoid corrosion and working fluid loss problems, and at the same time, through the phase change heat transfer of the working fluid, self-circulation is realized without additional pump power, and a larger temperature difference can be constructed to achieve efficient heat transfer.

[0006] The design of the ultra-long gravity heat pipe system has the following problems: (1) The evaporation section is too long, resulting in the working fluid being too deep in the heat pipe. Under the action of water pressure, the working fluid in the deep layer is subjected to a pressure higher than the saturated vapor pressure at the corresponding formation temperature, resulting in the inability to vaporize the working fluid, reducing the heat transfer efficiency. (2) Affected by the carrying limit, due to the small diameter of the heat pipe, the long steam flow path and the fast steam flow rate, the mutual friction between the gas and the liquid is significantly aggravated, causing the reflux working fluid to be convoluted by the steam to the top of the heat pipe, destroying the normal two-phase flow and limiting the heat transfer capacity of the heat pipe.

[0007] The present invention realizes stratified decompression of the working fluid in the evaporation section while ensuring normal reflux of the working fluid by constructing an evaporation section with a layered groove structure, thereby effectively avoiding the problem of limited heat transfer due to excessive hydraulic pressure, and constructs a fin structure between the outer wall, the groove and the steam pipeline, which effectively increases the heat exchange area of ​​the evaporation section while playing a supporting effect. Finally, a gas-liquid diversion device is constructed in the insulation section and the condensation section to realize gas-liquid diversion and reduce the influence of the carrying limit, thereby effectively improving the heat transfer performance of the heat pipe. Summary of the invention

[0008] In view of the above background and technical problems, the present invention provides a super-long gravity heat pipe design that overcomes the hydraulic effect and enhances heat transfer, effectively overcomes the influence of excessive hydraulic pressure on the super-long gravity heat pipe, and improves the heat transfer performance of the heat pipe through a fin structure, and finally constructs a gas-liquid diversion device, with the aim of achieving efficient exploitation of medium and deep geothermal energy.

[0009] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0010] A super-long gravity heat pipe for overcoming the hydraulic effect and enhancing heat transfer, the heat pipe comprising an evaporation section, characterized in that the evaporation section is designed as a multi-layer structure, each layer comprising an outer tube, an inner tube, a groove and a fin, the groove being arranged on the inner wall surface of the outer tube for communication between layers, one end of the fin being arranged on the outer wall surface of the inner tube, wherein the other end of at least a part of the fins is connected to the outer wall surface of the groove, the inner tube being a vertical through structure, a certain spacing being provided between the inner tubes of adjacent layers, and a connecting structure being provided between adjacent outer tubes.

[0011] Preferably, 2-3 grooves are provided in each layer and are evenly distributed along the circumference formed by the inner wall of the outer tube.

[0012] Preferably, the grooves of adjacent layers are staggered.

[0013] Preferably, adjacent layers are rotated by 30-60°, so that the grooves of adjacent layers are staggered by 30-60°.

[0014] Preferably, a gas-liquid diversion device is arranged in the insulation section, and the gas-liquid diversion device includes a diversion pipe, a support ring and a gas collecting ring. The diversion pipe is arranged in the outer pipe of the condensation end, and the support ring is arranged between the inner wall surface of the insulation section of the heat pipe and the diversion pipe; the gas collecting ring is arranged at the bottom of the insulation section, extending downward from the bottom of the diversion pipe toward the outer pipe, and there is a certain distance between the lowermost end of the gas collecting ring and the outer pipe; the gas collecting ring is located at the upper part of the inner pipe of the uppermost evaporation section, and the support ring is provided with a hole that passes through from top to bottom.

[0015] Preferably, a gas-liquid diversion device is provided in the condensation section, and the gas-liquid diversion device includes a diversion pipe and a liquid return ring. The liquid return ring extends downward and outward from the diversion pipe, and a channel designed for liquid reflux is provided between the outermost end and the outer tube of the condensation end; the diversion pipe is opened in the condensation section.

[0016] Preferably, the downward inclination angle of the liquid return ring is between 10 and 40 degrees.

[0017] Preferably, the downward inclination angle of the gas collecting ring is between 40° and 60°.

[0018] Each layer is an independent module structure, connected by splicing adjacent outer tubes.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The evaporation section adopts a layered structure design, which divides the evaporation section liquid pool into multiple sections. The groove structure is used to achieve connectivity between layers. When the upper liquid level reaches the expected range, it will flow along the groove to the next layer, avoiding the problem of the working fluid not being able to boil due to excessive hydraulic pressure, thereby improving heat transfer performance.

[0021] 2. The evaporator section adopts a finned support structure. The fins fix the outer tube, groove and inner tube, and at the same time significantly increase the heat exchange area between the working fluid and the wall of the heat pipe, effectively improving the heat transfer capacity of the heat pipe.

[0022] 3. The present invention adopts a layered and graded structure to achieve modular design. The evaporation section, the insulation section, and the condensation section are all spliced ​​and connected by unit levels. They can be spliced ​​arbitrarily according to different working conditions.

[0023] 4. The present invention adopts a gas-liquid diversion device to effectively avoid the interaction between gas and liquid and significantly enhance the carrying limit of the heat pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the present invention;

[0025] Figure 2 This is a partial enlarged view of the evaporation section of the present invention;

[0026] Figure 3 This is a structural view of each layer of the evaporation section of the present invention;

[0027] Figure 4 It is a schematic diagram of gas-liquid flow in the present invention;

[0028] Figure 5 It is a flow diagram of the condensation section of the present invention.

[0029] In the figure: 1-super long gravity heat pipe, 2-dividing pipe, 3-support ring, 4-gas collecting ring, 5-layered inner pipe, 6-groove, 7-super long gravity heat pipe base, 8-fin, 9-layered outer pipe, 10-liquid return ring, 11-opening DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention will be supplemented below with reference to the accompanying drawings in the embodiments of the present invention.

[0031] like Figure 1 As shown, an ultra-long gravity heat pipe 1 that overcomes the hydraulic effect and enhances heat transfer, the heat pipe is arranged in a vertical direction, and the heat pipe includes an evaporation section, which is located at the bottom of the heat pipe. Figure 1 , Figure 2 As shown, the evaporation section is designed as a multi-layer structure, each layer includes an outer tube 9, an inner tube 5, a groove 6 and a fin 8, the groove 6 is arranged close to the inner wall of the outer tube or arranged on the inner wall of the outer tube, for communication between layers, one end of the fin 8 is arranged on the outer wall of the inner tube, wherein the other end of at least a part of the fins is connected to the outer wall of the groove 6. The fin is used to connect the outer tube 9, the groove 6 and the inner tube 5 to achieve fixation. The inner tube 5 is a vertical through structure, there is a certain distance between the inner tubes 5 of adjacent layers, and the outer tubes 9 of adjacent layers are connected.

[0032] See also Figure 2 The bottom of the inner tube 5 is a through-type structure, which is used for steam to flow from the lower layer to the upper layer. The bottom of the groove 6 is also a through-type structure, which is used for liquid to flow from the upper layer to the lower layer. The rest of the positions are closed structures.

[0033] The evaporation section adopts a layered structure design, dividing the evaporation section liquid pool into multiple sections, and realizing the connection between layers through the groove structure. When the upper layer liquid level reaches the expected range, it will flow along the groove to the next layer, avoiding the problem of the working fluid not being able to boil due to excessive hydraulic pressure, and improving the heat transfer performance.

[0034] Preferably, Figure 1As shown, the insulation section is located in the middle, and a gas-liquid diversion device is arranged in the insulation section, the gas-liquid diversion device includes a diversion pipe 2, a support ring 3 and a gas collecting ring 4, the diversion pipe 2 is arranged in the outer pipe of the insulation end, the support ring is arranged between the inner wall surface of the insulation section of the heat pipe and the diversion pipe; the gas collecting ring is arranged at the bottom of the insulation section, extending from the bottom of the diversion pipe downward toward the outer pipe, and there is a certain distance between the lowermost end of the gas collecting ring and the outer pipe; the gas collecting ring is located at the upper part of the inner pipe of the uppermost evaporation section, and the support ring is provided with a hole that passes through from top to bottom.

[0035] Preferably, the condensation section is located at the upper part, and a gas-liquid diversion device is arranged in the condensation section, wherein the gas-liquid diversion device comprises a diversion pipe 2 and a liquid return ring 10, wherein the liquid return ring extends downward and outward from the diversion pipe, wherein a channel designed for liquid reflux is provided between the outermost end and the outer tube of the condensation end; the diversion pipe is opened 11 in the condensation section.

[0036] A gas-liquid diversion device is constructed in the insulation section and the condensation section, including a diversion pipe 2, a liquid return ring 10, a support ring 3 and a gas collecting ring 4, wherein the support ring 3 is arranged between the outer wall of the heat pipe insulation section and the diversion pipe to play a fixing role; the gas collecting ring 4 is arranged at the bottom of the insulation section to collect steam and provide a passage for the working medium to reflux; the liquid return ring 10 is arranged between the outer wall of the heat pipe condensation section and the diversion pipe 2 to design a channel for liquid reflux; the diversion pipe 2 is opened 11 in the condensation section. A fluid channel is arranged on the support ring 3.

[0037] It is divided into an evaporation section, an insulation section and a condensation section through a modular design, wherein the evaporation section adopts a layered design, and the ultra-long gravity heat pipe evaporation section absorbs the external deep geothermal energy to vaporize the working fluid in each layer, and the steam flows upward into the inner tube 5 along each layer, and then flows into the diversion pipe 2 of the gas-liquid diversion device through the gas collecting ring 4. After the steam flows into the condensation section, it flows into each condensation chamber through the opening 11 for condensation, and flows into the first layer of the evaporation section along the wall through the return liquid ring 10. As the working fluid page in the first layer gradually rises until it reaches the height of the groove 7, the working fluid flows into the next layer along the groove, and circulates until it flows into the base 7, and continuously circulates for heat transfer.

[0038] A groove 6 is provided between each layer of the evaporation section, and the groove 6 is used to control the height of the liquid level in each layer. When the refluxed working fluid gradually fills up the layers and reaches the opening of the groove 6, the working fluid will flow into the next layer along the groove 6, thereby realizing the layered decompression of the working fluid in the evaporation section and realizing the connection between the layers. Under the premise of ensuring the normal reflux of the working fluid, the influence of the hydraulic effect on the ultra-long gravity heat pipe is effectively avoided, and the heat transfer capacity of the heat pipe is enhanced.

[0039] Fins 5 are provided between each layer of the evaporation section, and are used to connect the outer tube 9, the groove 6 and the inner tube 5. While playing a fixing role, the fins 5 significantly increase the heat exchange area of ​​the evaporation section, enhance the heat transfer between the working fluid and the wall of the heat pipe, and enhance the heat exchange capacity of the heat pipe.

[0040] The heat pipe is provided with a gas-liquid diversion device in the condensation section and the insulation section. The steam transmitted by the evaporation section is first collected by the gas collecting ring 4, and the separation between the steam and the condensate is achieved through the diversion pipe 2, which effectively avoids the backflow of the working medium caused by the gas-liquid friction and improves the carrying limit of the heat pipe. The steam then flows into each condensation chamber through the condensation section opening 11 for cooling. By dividing the condensation chamber, the steam condensation is more uniform and the heat exchange capacity is enhanced. The condensed working medium flows back to the evaporation section along the outer wall of the heat pipe through the liquid return ring 10, and the condensed working medium is left along the outer wall to achieve faster heating and better vaporization heat exchange in the evaporation section.

[0041] Preferably, the height of the inner tube 5 is less than the height of the outer tube 9, and the height of the groove 6 is less than the height of the inner tube 5. The height of the inner tube 5 between each level is less than the height of the outer tube 9, such as Figure 4 In the steam flow path (solid arrow), the height of the inner tube 5 is lower than that of the outer tube 9 to leave space for the steam evaporated from the working medium in this level to flow into the steam channel, and then flow to the next level until it reaches the condensation section.

[0042] The height of each inter-stage groove 6 is smaller than the height of the inner tube 5. Figure 4 In the liquid flow path (hollow arrow), the height of the groove 6 is less than the height of the inner tube 5 to prevent part of the working fluid from flowing back along the inner tube 5 when the liquid level of the working fluid in this level accumulates to the height of the groove and flows back, thereby destroying the steam flow in the inner tube and causing the heat transfer to deteriorate. Therefore, the height of the groove 6 is lower than the height of the inner tube 5, so that all the working fluid flows along the groove into the next level.

[0043] The height of the inner tube 5 is 90-95% of the height of the outer tube 9. The above parameters only need to leave space for steam to flow into the steam flow channel of the inner tube, so that the heat pipe can achieve the best heat exchange effect.

[0044] The height of the groove 6 is 95-98% of the height of the inner tube 5. The groove 6 only needs to be slightly lower than the inner tube 5 so that the reflux medium flows along the groove to the next level. The above parameters can enable the heat pipe to achieve the best heat exchange effect.

[0045] Preferably, the height of each layer of the evaporation section is 5-15 meters, which is determined according to the saturated vapor pressure of different working fluids under ground temperature conditions. When the working fluid is water, the recommended height of each layer is 9-11 meters. The height of each layer of the insulation section is 5-15 meters. Since it is only used for steam flow, it can be selected according to specific working conditions. The height of each layer of the condensation section is 1-3 meters, which can be selected according to specific working conditions. The above parameters can enable the heat pipe to achieve the best heat exchange effect.

[0046] Preferably, each layer of grooves is provided with 2-4, preferably 3, uniformly distributed along the circumference formed by the inner wall of the outer tube. By providing multiple grooves, the downward flow of the liquid can be fully realized, and the heat transfer performance can be improved.

[0047] Preferably, the grooves of adjacent layers are staggered to ensure that the working fluid of the upper layer effectively flows into the lower layer, and when the working fluid of the lower layer reaches the entrance of the groove, the working fluid enters the lower layer in sequence.

[0048] Preferably, the adjacent layers are rotated 30-60 degrees, so that the grooves of the adjacent layers are staggered by 30-60 degrees. By setting the above optimized rotation angle, the effective flow of the upper layer working fluid into the lower layer can be further optimized. When the height of the lower layer working fluid reaches the entrance of the groove, the working fluid enters the lower layer in sequence.

[0049] Preferably, an insulation layer is provided inside the evaporation section of the heat pipe to reduce heat loss during the flow of steam.

[0050] Preferably, the diverter pipes 2 of the insulation section and the condensation section are also only insulation layers to reduce heat loss of steam during the flow process and ensure that the rising steam is heat transferred through the outer wall of the outer pipe of the condensation section.

[0051] Preferably, the inclination angle of the liquid return ring is 10-40°, that is, the angle between the liquid return ring and the horizontal plane is 10-40°.

[0052] Preferably, the inclination angle of the gas collecting ring is 40-60°, that is, the angle between the gas collecting ring and the horizontal plane is 40-60°.

[0053] Preferably, the length of the ultra-long gravity heat pipe ranges from 200 to 5000 m.

[0054] Preferably, the length of the evaporation section ranges from one third to two thirds of the total length, the length of the insulation section ranges from one third to two thirds of the total length, and the condensation section is the part on the surface used for heat exchange, and its length ranges from 2 to 10 meters.

[0055] As a preference, the fin spacing is recommended to be controlled within the range of 0.1 to 0.3 m, which effectively increases the heat transfer area while ensuring smooth steam flow in the evaporation section.

[0056] Preferably, the shape of the fins may be arc, triangle, square, etc., and openings may be designed on the fins.

[0057] Preferably, the working fluid in the heat pipe can be an organic working fluid or an inorganic working fluid such as deionized water, acetone, ammonia water, ethanol, etc.

[0058] As a preferred method, the vacuum degree of the ultra-long gravity heat pipe is 10 -1 ~10 -6Pa.

[0059] Preferably, the liquid filling rate of the super-long gravity heat pipe is between 10% and 40%.

[0060] As an improvement, the evaporation section is arranged in the geothermal to extract geothermal heat sources.

[0061] As an improvement, the height of the grooves in different layers is getting smaller and smaller from bottom to top. This is because the experiment found that the phenomenon of liquid not being able to boil becomes more and more obvious from bottom to top. By setting the height of the grooves to be smaller and smaller, the upper liquid can flow to the lower part as quickly as possible, and not too much liquid will accumulate, thereby reducing the problem of the working fluid not being able to boil due to excessive hydraulic pressure and improving the heat exchange effect.

[0062] As an improvement, the heights of the grooves of different layers are gradually increasing from bottom to top. The above amplitude variation is also found through a large number of experiments, which can further avoid the problem that the working fluid cannot boil due to excessive hydraulic pressure.

[0063] Compared with the prior art, the present invention has the following advantages:

[0064] 1. The evaporation section adopts a layered structure design, which divides the evaporation section liquid pool into multiple sections. The groove structure is used to achieve connectivity between layers. When the upper layer liquid level reaches the expected range, it will flow along the groove to the next layer, avoiding the problem of the working fluid not being able to boil due to excessive hydraulic pressure, thereby improving heat transfer performance.

[0065] 2. The evaporator section adopts a finned support structure. The fins fix the outer tube, groove and inner tube, and at the same time significantly increase the heat exchange area between the working fluid and the wall of the heat pipe, effectively improving the heat transfer capacity of the heat pipe.

[0066] 3. The present invention adopts a layered and graded structure to achieve modular design. The evaporation section, the insulation section, and the condensation section are all spliced ​​and connected by unit levels. They can be spliced ​​arbitrarily according to different working conditions.

[0067] 4. The present invention adopts a gas-liquid flow splitter to effectively avoid the interaction between gas and liquid, and significantly enhance the carrying limit of the heat pipe. The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the scope of protection of the present invention.

[0068] 5. By setting the height variation of the grooves of different layers in the direction from bottom to top, the problem of the working fluid not being able to boil due to excessive hydraulic pressure can be further reduced, thereby improving the heat exchange effect.

Claims

1. An ultra-long gravity heat pipe for overcoming hydraulic effect and enhancing heat transfer, the heat pipe comprising an evaporation section, characterized in that: The evaporation section is designed as a multi-layer structure, each layer includes an outer tube, an inner tube, a groove and a fin. The groove is arranged close to the inner wall surface of the outer tube or on the inner wall surface of the outer tube for communication between layers. One end of the fin is arranged on the outer wall surface of the inner tube, wherein the other end of at least a part of the fin is connected to the outer wall surface of the groove. The inner tube is a vertical through structure, with a certain spacing between the inner tubes of adjacent layers, and adjacent outer tubes are connected together; a gas-liquid diversion device is arranged in the condensation section, and the gas-liquid diversion device includes a diversion pipe and a liquid return ring, and the liquid return ring extends downward and outward from the diversion pipe, wherein a channel designed for liquid reflux is provided between the outermost end and the outer tube at the condensation end; the diversion pipe is opened in the condensation section; each layer is an independent module structure, which is connected by splicing adjacent outer tubes; along the direction from bottom to top, the height of the grooves of different layers becomes smaller and smaller; along the direction from bottom to top, the height of the grooves of different layers becomes smaller and smaller and increases continuously.

2. The ultra-long gravity heat pipe according to claim 1, characterized in that: Each layer of grooves is provided with 2-3 grooves, which are evenly distributed along the circumference formed by the inner wall of the outer tube.

3. The ultra-long gravity heat pipe according to claim 1, characterized in that: The grooves of adjacent layers are staggered.

4. The ultra-long gravity heat pipe according to claim 1, characterized in that: Adjacent layers are rotated 30-60°, so that the grooves of adjacent layers are staggered 30-60°.

5. The ultra-long gravity heat pipe according to claim 1, characterized in that: A vapor-liquid diversion device is arranged in the insulation section, and the vapor-liquid diversion device includes a diversion pipe, a support ring and a gas collecting ring. The diversion pipe is arranged in the outer pipe of the insulation end, and the support ring is arranged between the inner wall surface of the insulation section of the heat pipe and the diversion pipe; the gas collecting ring is arranged at the bottom of the insulation section, extending downward from the bottom of the diversion pipe toward the outer pipe, and there is a certain distance between the lowermost end of the gas collecting ring and the outer pipe; the gas collecting ring is located at the upper part of the inner pipe of the uppermost evaporation section, and the support ring is provided with a hole that passes through from top to bottom.

6. The ultra-long gravity heat pipe according to claim 1, characterized in that: The downward inclination angle of the liquid return ring is between 10 and 40 degrees.

7. The ultra-long gravity heat pipe according to claim 1, characterized in that: The downward inclination angle of the gas collecting ring is between 40 and 60 degrees.

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